Low-water alarm



Patented July Y19, 1927.

UNITED STATES NORMAN M. BAKKER, 0F CLEVELAND, OHIO.

LOW-WATER ALARM.

Application led yOctober 22, 1324. Serial No. 745,242.

My invention relates to a temperature controlled mechanism and has specifically in view the provision of a low water alarm for locomotive boilers.

In my prior Patent No. 1,496,614, issu-ed June 3, 1924, I have disclosed an'arrangement utilizing a body of fusible material which will melt at a predetermined water level and thereby cause the operation of an alarm to warn the engineer.

The improvements embodied in the present application are to be used with a device of the character covered by my prior patent. However, some of the improvements are of general application and can be utilized in other types of low water alarms.

One of the objects of the invention is to provide a construction whereby the fusible element or similar heat responsive member can be connected to the crown sheet in such a manner so that it will be substantially insulated therefrom, whereby the heat from combustion can be conducted through the water to a point above the water without substantial heat loss to the water.

Another object is to provide a means to shield the fusible plug-holding element from the cooling effect of the water contained in the moist steam at the surface of the boiling water.

A further object is to provide means for con'ipensating for the different expansion of various parts.

A further object is to provide a locking device for the tool which is used in resetting the device.

A still further object is to provide valve for testing the alarm in order to see that it is in operative condition.

Another object is to provide a valve, the seat of which can be readily reground.

With these and other' objects in view, my invention consists of certain novel and peculiar features of construction and combination of parts as will be hereinafter more fully described and particularly pointed out in the claims.

In the drawings: p

Fig. 1 is a vertical section of the low water alarm in position for use;

Fig. 2 is a detail elevation of the upper end of the alarm; and

Fig. 3 is a fragmentary vertical section of 5 the preferred form of protecting jacket.

Referring more particularly Vto thedrawings, 2'is-the crown sheet and 1 is` the wrapper sheet of a boiler. Tapped into the wrapper sheet is a stuffing box 3 and tapped into th-e crown sheet is a shell 4. Passing through the shell 4 and supported thereby is the heat conducting member 5 provided at itsy upper end with a chamber 6 for holding the fusible metal 7 and at its lower end with a removable cap 8, made of Monel metal, refractory material, or any suitable nut 14. The insulation provided by the air space 9 may be sufficient in itself to accomplish the desired result. However, when the asbestos packing rings are used, more complete insulation is had, so that the` fusible metal will melt with more water over the crown sheet, than if the packing rings are omitted.

It will be noted that the bottom ofthe fusible material chamber 6 is above the insulated point of contact, as represented by the flange 10. This arrangement insures that the fusible material 7 will remain solid as long as the water is above the insulated point of contact, since the water acts directly on the exterior of the fusible material chamber 6.

When the water drops below this insulated point of contact, the relatively complete insulation of the shell 4 from the heat conducting member 5 permits a rapid rise in temperature of the fusible material chamber 6, thus melting the fusible material as quickly as possible. u

When the water in the boiler drops to a level where it will no longer cool the upper endl of the heat conducting member 5, there will be no cooling effect therefrom upon the fusible metal and allt-he heat which is being put into the member 5 will be transmitted along such member to the lfusible metal.

lil?,

Very soon after the water' has fallen to the v said' level, 'the' alarm will 'Operate and in the particular arrangements" Shown, While thereY s still from about-'one and a half t0 four and a half` inches of water over the crown sheet.

Immediately above the surface of, the

water in the boiler, the steam is very moist. This moist steam has practically the same cooling effect as the water in the boiler, and if no protection is afforded to the upper end of the member 5, the moist steam will tend to keep the temperature et the said member suiliciently low to prevent melting ot the fusible plug even after the water has dropped below the desired level. In order to avoid this situation, I surround the upper portion of the member 5 with a jacket so that the moist steam, due to the tact that as the bubbles ot' steam rise to the snrlace of the water, they burst, thus causing spray, which is very high in cooling quality, will not come in contact with the upper porlion of the member In the Jforni ot jacket shown in Fig. 1, the upper and lower ends ot' the jacket are pern i'orated at 16 to permit water to circulate within the jacket when the jacket is surrounded by water.

In the form shown in Fig. 3, the jacket 15 is made integral with the .nut 14s and is open at the top and not perforated at the bottom.

In the form shown in Fig. 1, as soon as the water falls to a level below the perforatious 16 in the bottom oit shell 15, the fusible metal will melt.

In the llorm shown in Fig. 3, the fusible metal will melt slowly after the water has dropped below the top of the jacket 15.

The heat capacity of the member 5 when insulated is so related to the quantity ot' :fusible metal that the alarm will operate while a substantial quantity of water is still over the crown sheet.

The operating plunger 17 is provided on its lower endwith a screw thread 18, which is supported by and embedded in the `fusible metal T. '.l`hreaded on the uppr end of the member 5 is the tube 1S) which is in tight but expansible engagement with the stuli'- ing box 3 and which is threaded at itsI upper end te receive the housing 20. Screwed into the top ot the housing is the bushing' 21, having an aperture 29, therethrough for thc valve rod 23. Screwed onto the nut 2l is the valve casing 2li, the inlet port Q5 being connected to the steam chamber through the pipe 26 and the outlet port 27 being connected to the whistle 28. The valve seat 29 is threaded in the body of the valve and has an operating handle 30 at its upper end. To test the valve, it is merely necessary to screw the valve seat olf of the valve head Q3, whereupon steam will pass therethrough, showing the device is in operative condition.

It will be noted that the tube 19, housing and valve casing 24 are united into one piece. Then heat strikes the same before it does the operating plunger 17, a greater expansion occursv with the result that the valve seat will be lifted off of the valve head,

Lasalle thereby permitting leakage until later, the plunger is heated to the same temperature as the tube, when it in turn will expand, and after the tube has reached its limit of expansion. To take care et this differential expansion, I interpose a compensating spring 3l between the valve rod 223 and the upper end of the operatingl plunger 17. IVith this Construction, the valve 23 will always be held i'irmly against its seat, regardless of' difterence in expansion ot the outside and inside members.

The spring 3l also provides a means to assist in regrinding the valve. The valve rod is provided with guides 32 and when it is desired 'to grind the valve, this can be done by merely turning the handle of the valve seat back and Forth against the pressure of the spring 3l, the vuides preventing rotation ot the valve rod.

Tvlithin the housing 21) is the compression spring 323, which exerts a contimious downward prefsure on the operating plunger through the medium of the collar 34.

In operation, when the fusible metal melts, plunger 17 is forced downward by the pressure of the spring .33 thereby movingl the valve rod Q3 ot'f ot the valve seat 29 and pern'iitting steam to pass from the boiler to the alarm whistle. Then the temperature of the fusible material is reduced by the water reaching the proper level in the boiler, the fusible material solidii'ics around the screw-threzuled end ol the oper' ating plunger'.

For resetting the operating plunger, it is provided with a squared portion 35, ii'or engagement with a wrench 36. On turning the operating stem. on account of its threaded engagement with the fusible plug, it will be elevated against the pressure ol the spring 33 to move the valve stem to closed position and thus shut oil the passage ot steam from the boiler to the alarm. The aperture in the housing is closed by the collar B7. which is held to the housing` by means of a bayonet. joint, the lugs 38 passing through au aperture in the shoulder Si) and then being turned to position so as to rest thereon. The wrench 3G passes througli an ear l0 on the housing and an ear Lll on the collar 37 and this locks the two against rotation. The end of the wrench is pro vided with a slot 42 to hold a seal. The wrench cannot be withdrawn without breaking the seal and in this manner a check is kept on whether or not the alarm has operated.

What I claim is:

l. In a device of the character described, a heat conducting member, means for supporting said member in the crown sheet of a boiler, a heat responsive device carried by the upper end of the heat conducting member and wholly disposed at a distance above lou the crown sheet oit the boiler comparable to l the predetermined water level at which the Il U device shall operate, the said heat responsive device being in heat conducting relation with the surrounding water, the portion of the heat conducting member below the said rcsponsive device being substantially heat insulated from the surrounding water.

2. In a device of the character described, a shell connected to the crown sheet of a boiler, a heat conducting member arranged in said shell and supported thereby, the said member being substantially heat insulated from the shell, and a heat responsive device carried by the heat conducting member, the said device being located above the insulated portion of the heat conducting member.

3. In a device of the character described, a heat conducting member, a chamber carried by the upper end of the said member, fusible material in the said chamber, the said material adapted to remain solid only as long as water is in contact with ythe walls of said chamber and means for insulating the heat conducting member from the cooling effect of the water below the said chamber.

i. In a device of the character described a shell connected to kthe crown sheet 'tot a boiler, a heat conducting member arranged in said shell and supported thereby, the said member being substantially heat insulated from the shell, and a heat responsive device carried by t-he heat conducting member, the said device being located at a point above the point of contact betweenthe heat conducting member and the shell.

5. In a device ot the character described, a shell carried by the crown sheet of a boiler, a heat conducting member located therein, the said member having a shoulder resting on the shell and heat insulating packing between said shoulder and shell.

6. In a device of the character decribed, a shell carried by the crown sheet of a boiler, a heat conducting member provided with a shoulder resting on the upper end of the shell, heat insulating packing between said shoulder and shell, the heat conducting member being spaced from the shell to provide an insulating air space, and a heat responsive device above the said shoulder.

7. In a device of the character described, a heat conducting member provided with a heat responsive device at its upper end and located above the crown sheet, means for substantially heat-insulating the said member from the crown sheet, and means for protecting the upper end of the heat conducting member from the cooling effec-t of moist steam and comprising a jacket surrounding the said heat-conducting member.

8. In a device of the character described, a heat conducting member provided with a heat responsive device at its upper end and located above the crown sheet, means for substantially heat insulating the said member from the crown sheet and means for protecting the upper end of the heat conducting member from the cooling eifect of moist steam.

9. In a device of the character described, a heat conducting member provided with a heat responsive device at its upper end and located above the crown sheet, means for substantially heat insulating the said member from the crown sheet, a nut for securing the heat conducting member in position and a jacket carried by the nut and spaced from the said upper end to protect it from the cooling effect of moist steam.

l0. In a device of the character described, a body provided with a heat responsive device, a plunger operatively connected therewith and provided with a valve, a tube surrounding the i plunger and having a passage provided with a valve seat, and means for normally holding said valve on said seat,

said means comprising means for compensating the difference in expansion between the rod and tube.

11.y In a device of the character described, a body provided with a heat responsive device, a plunger operatively connected therewith and provided with a valve, a tube surrounding the plunger and having a passage provided with a valve seat and means for normally holding said valve on said seat, said means comprising means for compensating the difference in expansion between the rod and tube, and comprising a spring interposed between the valve stem and plunger.

12. In a device of the character described, a body provided with a heat responsive device, a valve, a valve seat cooperating wgith the said valve, the valve being resilicntly supported and normally held seated by said heat-responsive device, and means to prevent rotation of the valve as the seat is rotated.

13. In a device of the character described, a body provided with a heat responsive device, a plunger operated thereby, to open a valve to permit escape of steam, a valve seat, and means for independently operating the valve by movement of the valve seat.

In testimony whereof I aiix my signature.

NORMAN M. BAKKER. 

